1. Field of the Invention
The present invention relates to a wire spring forming apparatus which manufactures a wire spring having various shapes by holding a wire to be formed into the wire spring between pressure feed rollers, pressure feeding the wire on the basis of a rotation of the pressure feed rollers and forcibly applying a process such as a bending process, a curving process or the like to the wire by forming tools radially arranged around an axis of a quill guiding the wire at a position where the wire comes out from the front end of the quill, and more particularly to a wire spring forming apparatus which can twist the wire so that a direction of the wire coincides with a forming direction of the forming tools by a small moment of inertia.
2. Description of the Conventional Art
As the wire spring, there are required structures to which a process such as a bending process, a curving process or the like is applied so as to give various kinds of shapes in correspondence to intended uses thereof. As a result, in conventional, Japanese Unexamined Patent Publication No. 10-29028 discloses a wire spring forming apparatus which manufactures a wire spring having various shapes by mounting forming tools radially arranged around a center line of a quill guiding a wire to be formed into the wire spring on a rotary tooling table so as to turn the forming tools at a desired angle around the center line of the quill, and forcibly applying a process such as a bending process, a curving process or the like from a desired direction by the forming tools turned together with the rotary tooling table at a position where the wire comes out from the front end of the quill.
However, in this wire spring forming apparatus, since it is necessary to turn the rotary tooling table to which a plurality of comparatively heavy forming tools are mounted, around the center line of the quill, a great power source is required. Further, when it is intended to apply the process such as the bending process, the curving process or the like to the wire so as to give the various kinds of shapes as mentioned above, not only the number of the forming tools mounted to the rotary tooling table is necessarily increased, but also a turning angle of the rotary tooling table is increased, so that it is impossible to turn the rotary tooling table for a short time. Accordingly, there is a disadvantage that it is impossible to efficiently manufacture the wire spring.
Accordingly, in order to solve the disadvantage mentioned above, Japanese Patents Nos. 2551525 and 2939472 disclose apparatuses each of which can twist a wire by revolving rotated pressure feed rollers corresponding to a pressure feeding means of the wire around a center line of the wire in the state of holding the wire between the rollers, by a revolving means and can change a position at which the process such as the bending process, the curving process or the like is applied to the wire to a direction in which a desired forming tool is positioned so as to pressure feed to a front end of a quill.
However, both of the apparatuses are structured such that the rotated pressure feed rollers corresponding to the pressure feeding means of the wire are firmly fixed to the front end portions, which protrude to the external of a box-shaped housing, of rotated shafts rotatably supported by bearings which are provided in the front surface and the rear surface within the box-shaped housing, thereby holding the wire between the rollers. Accordingly, the axis of revolution exists outside the box-shaped housing provided therein with a power transmitting means for transmitting a drive force from a drive source to the pressure feed rollers, and the structure is made such that the axis of revolution is biased to one side.
Then, since both of the apparatuses are, as mentioned above, of a type in which the drive source (servo motor) of the rotated pressure feed rollers corresponding to the pressure feeding means of the wire is placed out of the revolving means and is not revolved, the pressure feed rollers rotate (rotate around their own axes) at an angle in proportion to an angle of revolution and the wire is moved in a pressure feeding direction or a reverse direction to the pressure feeding direction when revolving the pressure feed rollers on the basis of a differential phenomenon between a gear assembled so as to be revolved within the revolving means in a transmission gear train corresponding to the power transmitting means for transmitting the drive force to the pressure feed rollers and a gear out of the revolution, so that there is a disadvantage that it is required to do an operation of correcting and setting a value of pressure feed amount of the wire repeatedly while confirming a shape of a product at every time of revolving the pressure feed rollers, for setting up the wire spring forming. In particular, since the wire is frequently pressure fed while the wire is twisted or twisted back by the revolution with being pressure fed by the pressure feed rollers, there is a disadvantage that further much time is required for setting up the forming process.
Further, since both of the apparatuses employ a combination of gears in which the direction of transmission becomes 90 degrees, in addition to a coaxial rotation transmitting mechanism for revolving and pressure feeding the wire, along the axis of revolution, there are disadvantages that a structure of a whole of the apparatus is complex, a blade number of the gears is much, a number of the members is increased, and the apparatus becomes expensive.
Further, as a fateful disadvantage of both of the apparatuses, since the axis of revolution exists out of the box-shaped housing provided therein with the power transmitting means for transmitting the drive force to the pressure feed rollers, a center point of gravity of the box-shaped housing and the power transmitting means provided in the box-shaped housing to transmit the drive force to the pressure feed rollers is far from the axis of revolution and is biased to one side, so that the moment of inertia accompanying with the revolution is significantly great. As a result, since a vibration accompanying with a positioning at a time of the revolution is also increased, a drive source having a large capacity is required for the revolving means, and further it is necessary to keep an acceleration of rotation at a time of positioning at the revolving time to be gentle, so that there is a disadvantage that an efficiency of forming the wire spring becomes very low.